Detroit Sheds Pounds for Gas-Mileage Gains

By

Neal E. Boudette and

Mike Ramsey

Updated Jan. 14, 2013 10:21 a.m. ET

DETROIT—Auto makers wrestling with ambitious mileage goals have touted hybrids and electrics as the wave of the future, but they have found a quicker path to improved fuel efficiency, reinventing the way traditional gas-powered cars are built.

For the past century, autos were made largely of steel. But pressed to produce cars and trucks that go farther on a gallon of gas, manufacturers gathering here this week for the Motor City's...